This invention relates to a liquid-permeable topsheet made of thermoplastic resin used for body fluid absorbent articles such as disposable diapers and sanitary napkins.
Conventionally, nonwoven fabric, perforated thermoplastic sheet or the like has been used as a liquid-permeable topsheet covering an absorbent core of body fluid absorbent articles.
Obviously it is desired that body fluid absorbency of such articles should be as rapid as possible and this will be effectively achieved, for example, by orienting flow of the body fluid on a topsheet or by controlling a diffusion of the body fluid in a predetermined direction so that the body fluid may rapidly spread over the entire surface of the absorbent core. While a topsheet made of nonwoven fabric is preferable in that a certain degree of diffusion can be expected under a capillary effect occurring between component fibres of the nonwoven fabric and the body fluid, it is difficult to realize rapid and direction-controlled diffusion of the body fluid since density of the nonwoven fabric for such application is limited by a requirement that a touch of the topsheet should be soft for user's skin. When the perforated sheet is employed as the topsheet, on the other hand, the body fluid smoothly flows on the sheet surface but can not be direction-controlled.
Accordingly, it is an object of the invention to provide a liquid-permeable topsheet made of thermoplastic resin so improved that a unique rib structure thereof allows a flow of body fluid to be controlled in a predetermined direction.